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Beams may be designed to be larger than required for strength consideration owing to aesthetics or other reasons. As such, the corresponding steel ratio is very low and the moment capacity of pure concrete section based on the modulus of rupture is higher than its ultimate moment of resistance. As a result, reinforcement yields first and extremely wide cracks will be formed. A minimum area of reinforcement is specified to avoid the formation of wide cracks.
Open stirrups are provided principally to resist shear forces in concrete beams and they are applied in locations in which the effect of torsion is insignificant.
Hot dip galvanizing protects steel/iron from corrosion by:
(i) It forms a metallic zinc and zinc-iron alloy coating on top of steel surface. This zinc coating reacts with moisture in atmosphere to from zinc salts which act as an insulating layer for steel/iron.
Stainless steel refers to alloy steels with more than 10.5% of chromium and consists of several groups like austenitic, ferritic, martensitic etc. Austenitic stainless steel is normally used in structural applications because of its high corrosion resistance. Austenitic and ferritic types of stainless steel cover about 95% of stainless steel applications. Stainless steel is not stainless although it is corrosion resistant under a wide range of conditions.
When structural steelworks are connected to the foundation, pedestals are normally designed to carry loads from metal columns through the ground surface to the footings which are located below the ground surface. With the installation of pedestals, it is the pedestals, instead of metals, which come into contact with soils.
The surface of footings is normally quite rough so that some leveling has to be carried out for the base plates. The interface between the base plates and footings after leveling is subsequently filled with grout.
In a typical painting system, there are normally three main layers, primer, undercoat and finishing coat. The primer acts as the first coat of the painting system and adheres to the substrate. It serves to provide a foundation for other coats. The mid-coat, undercoat, is designed to increase the film thickness and hinder the background colour. Moreover, it aids in the reduction of permeability by incorporating pigments like micaceous iron oxide. Finally, the finishing coat contributes to the appearance of the painting system like colour. Sometimes, it may be designed to provide additional abrasive resistance. However, in terms of corrosion protection to steelworks, it does not add much value.
Owing to the high thermal conductivity of steel, the temperature of unprotected steel is almost the same as the temperature of fire. Since the yield strength of structural steel drops approximately by half when its temperature rises to about 550oC, it is usually provided with some forms of insulation.
Corrosion inhibitors are chemical substances that, when added in small concentrations, stop or reduce the corrosion or reaction of the metal with the environment. It normally functions by one or more of the following mechanisms:
(i) It may alter the external environmental conditions by taking away or inactivating an aggressive agent;
